Featured Research

from universities, journals, and other organizations

Plants Grow Spindly When Reaching For Sunlight: Now Researchers Understand How

Date:

April 8, 2008

Source:

Salk Institute

Summary:

Those spindly plants that desperately try to reach for a break in the canopy formed by larger plants all suffer from the same affliction: Shade avoidance syndrome or SAS. Now, the molecular details of SAS have been brought to light.

Share This

Plants can tell the difference between the shade of an inanimate object and the shade of another plant. When a plant detects competition from neighboring plants, it initiates a set of responses, called collectively the shade avoidance syndrome, that alter its growth and physiology. A rapid and transient increase of newly synthesized auxin via a newly discovered auxin synthesis pathway allows plants to elongate and grow toward the sun.

Those spindly plants that desperately try to reach for a break in the canopy formed by larger plants all suffer from the same affliction: Shade avoidance syndrome or SAS. Now, the molecular details of SAS have been brought to light by researchers at the Salk Institute for Biological Studies.

Related Articles

To step out of their neighbors' shade, plants switch on a natural chemical factory for the synthesis of the plant growth hormone auxin that lets a plant grow and ultimately stretch toward the sun, the Salk researchers report in an article published in the April 4, 2008 issue of the journal Cell. Understanding this response at a molecular level will allow scientists to naturally manipulate this response to increase yield in crops ranging from rice to wheat.

"Plants compete with each other for light, and shade avoidance syndrome has a big ecological and economic impact, especially in the high density plantings typical of modern agriculture," says Howard Hughes Medical Institute investigator Joanne Chory, Ph.D., a professor in the Plant Biology, who led the study. "Suppressing the shade avoidance reaction in crops may allow us to increase biomass and seed yield."

Plants can sense and respond to the presence of other plants in their neighborhood by the relative increase in incoming far-red light resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants.

To secure their place in the sun, plants direct their growth resources toward stem elongation and away from bulking up harvestable portions such as leaves and seeds. "If all else fails, the plants put out what I like to call a premature 'desperation flower' to produce at least a couple of seeds that might find better growing conditions during the next season," explains Chory.

In an earlier study, Chory had confirmed the existence of a separate molecular pathway that plants use to adjust their growth and flowering time to shade. But the molecular events linking the detection of changes in light quality to changes in growth patterns were still poorly understood.

To identify genes that are involved in the shade avoidance syndrome, first author Yi Tao, a postdoctoral researcher in Chory's lab, searched a collection of mutated Arabidopsis thaliana seedlings for plants that no longer responded to crowded growth conditions. Like many commercially grown crops, Arabidopsis -- the lab rat of plant biologists -- doesn't tolerate shade well.

She identified a handful of genes that play a role in the shade response, one of which encoded an enzyme similar to alliinase, the enzyme that produces the characteristic flavor of onion, garlic and other members of the Alliaceae plant family. To predict the function of the newly identified enzyme, Chory turned to her Salk colleague Howard Hughes Medical Institute investigator Joseph P. Noel, Ph.D, director of the Jack H. Skirball Center for Chemical Biology and Proteomics.

Although Arabidopsis lacks garlic's pungency, Noel could model the newly discovered enzyme's structure based on the already-known, three-dimensional structure of alliinase. "The active site chemically resembled a nook and cranny likely to bind the amino acid tryptophan," says Noel. "That's when it became really exciting since we knew that plants can use tryptophan to synthesize auxin."

After virtual biochemistry led the way, real-life biochemistry confirmed that the enzyme indeed uses tryptophan to catalyze the first reaction in a three-step auxin-synthesis pathway and the new enzyme became known as tryptophan aminotransferase of Arabidopsis, or TAA1 for short.

Despite the importance of auxin for plant growth and development, the details of how auxin is synthesized continue to puzzle plant biologists. Multiple biochemical pathways for the production of auxin have been identified or proposed but the specific function of each pathway and how they intersect is not known. Now, the role of at least one pathway has become clearer.

"When the major photoreceptor for shade avoidance detects neighbors, it triggers the TAA1 pathway resulting in a rapid increase in free auxin, which is transported to sites in the stem where it can participate in the growth response," explains Chory. "Although we showed earlier that at least two additional biosynthetic routes to auxin exist in Arabidopsis, these other pathways are unable to compensate for the loss of the TAA1-dependent pathway."

In addition to Yi Tao, researchers who contributed to the study include post-doctoral researcher Lin Li, Ph.D., bioinformatics specialist Fangxin Hong, Ph.D. graduate student Lauren J. Ivans, research assistant Jason Lim, and assistant professor Jeff A. Long, all in the Plant Biology Laboratory at the Salk, postdoctoral researchers Jean-Luc Ferrer, Ph.D., and Florence Pojer, Ph.D., and lab manager Marianne E. Bowman, all in the Jack H. Skirball Center for Chemical Biology and Proteomics at the Salk Institute, professors Karin Ljung, Ph.D., and G๖ran Sandberg, Ph.D., both at the Umeๅ Plant Science Centre at the Swedish University of Agricultural Sciences in Umeๅ, Sweden, graduate student Javier E. Moreno and professor Carlos L. Ballar้, Ph.D., both at the Instituto de Investigaciones Fisiologicas y Ecologicas Vinculadas a la Acricultura in Buenos Aires, Argentina, postdoctoral researcher Youfa Cheng, Ph.D. and assistant professor Yunde Zhao, Ph.D., both in the Division of Biological Sciences at the University of California, San Diego.

Story Source:

The above story is based on materials provided by Salk Institute. Note: Materials may be edited for content and length.

More From ScienceDaily

More Plants & Animals News

Featured Research

Mar. 3, 2015  While studying a ground-nesting bird population near El Reno, Okla., a research team found that stress during a severe weather outbreak of May 31, 2013, had manifested itself into malformations in ... full story

Mar. 3, 2015  The 3-D printing scene, a growing favorite of do-it-yourselfers, has spread to the study of plasma physics. With a series of experiments, researchers have found that 3-D printers can be an important ... full story

Mar. 3, 2015  Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Mar. 3, 2015  By examining the forces that the segments of mosquito legs generate against a water surface, researchers have unraveled the mechanical logic that allows the mosquitoes to walk on water, which may ... full story

Mar. 3, 2015  Pediatric otolaryngologists and surgeons are concerned with parents getting the wrong message regarding the safety/desirability of letting babies and young children eat peanuts to prevent them from ... full story

Mar. 3, 2015  Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015  Similar to humans and animals, plants possess an innate immune system that protects them from invading pathogens. Molecular structures that only occur in pathogens enable their recognition and ... full story

Mar. 3, 2015  For almost a century, scientists have been puzzled by a process that is crucial to much of the life in Earth's oceans: Why does calcium carbonate, the tough material of seashells and corals, ... full story

Mar. 3, 2015  To simulate chimp behavior, scientists created a computer model based on equations normally used to describe the movement of atoms and molecules in a confined space. An interdisciplinary research ... full story

Featured Videos

Rare Goblin Shark Found in Australia

AFP (Mar. 3, 2015)  A goblin shark, a rare sea creature described as an &apos;alien of the deep&apos; is found off Australia and delivered to the Australian Museum in Sydney. Duration: 01:25
Video provided by AFP

Zookeepers Copy Animal Poses In Hilarious Viral Photos

Buzz60 (Mar. 2, 2015)  Zookeepers at the Symbio Wildlife Park in Helensburgh, Australia decided to take some of their favorite animal photos and recreate them by posing just like the animals. Jen Markham (@jenmarkham) has the story.
Video provided by Buzz60

Related Stories

July 1, 2012  Plant scientists have imaged and analyzed, for the first time, how a potted plant's roots are arranged in the soil as the plant develops. In this study,biologists also found that doubling plant ... full story

Apr. 24, 2012  A new project is being conducted by European researchers to plant the seeds for possible gardening on Mars on day. The plan for the future will be to grow first vegetables on Earth in a closed ... full story

Apr. 16, 2012  Mild mannered though they seem, plants are extremely competitive, especially when it comes to getting their fair share of sunlight. Whether a forest or a farm, where plants grow a battle wages for ... full story

Mar. 15, 2011  The world of a plant can be a stressful place. Many plants constantly compete with their neighbors for light by elongating to try and get out of their shade. In crops, this elongation can ... full story

Dec. 17, 2010  Plants that "lose the battle" during competitiveness for light because they are shaded by larger neighbours, counteract. They adapt by rapid shoot elongation and stretch their leaves ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.